Good defense is about talent and scheme. Just about every coach will tell you the former is more important than the latter, as winning one-on-one battles is the foundation of good defense. But to be great, a defense needs both.
California had neither last year. So, yeah, it was a defensive disaster.
Disaster? The Bears yielded 42.6 points per game, which ranked 127th -- second to last -- in the nation. To call their run defense milquetoast is to do an injustice to Caspar Milquetoast, the "Timid Soul" of the Harold T. Webster comic from the 1920s.